Medical cannabis is legal, but the 2mcg/L THC limit is a strict roadside...
https://www.protopage.com/wade-lopez06#Bookmarks
Medical cannabis is legal, but the 2mcg/L THC limit is a strict roadside reality. While a medical defence exists, it isn't immunity; ensure the DVLA clears your fitness. Legality is no substitute for responsibility: if impaired, don't drive.